On the heat budget of the Arabian Sea

Summary The rate of oceanic heat storage of the upper 200m of the Arabian Sea is explained in terms of net air-sea heat flux (Q _F), heat change due to horizontal divergence and vertical motion (Q _V) and heat change due to lateral advection (Q _A). The analysis revealed that the heat storage of the Arabian Sea is mainly controlled byQ _V while the effect ofQ _A is much larger than expected. Parameterisation of summer cooling revealed that the depletion of energy from the mixed layer is mainly due to upwelling and horizontal advection though large amount of heat is accumulated due to net air-sea heat flux. The annual heat balance of the upper 200m of the Arabian Sea suggested large heat gain by air-sea exchange processes. About two third of this heat gain is compensated by horizontal advection and one third by vertical advection.With 4 Figures     

Modeling hydrodynamics and aquaculture waste transport in coastal maine

Net-pen aquaculture results in the introduction of excess fish food and fecal matter in coastal waters. These wastes may modify the benthic environment. Mathematical models are developed in this study to simulate tidal and wind-driven currents, waves, and the resulting dispersion of fish food and fecal matter in coastal Maine, a region where limited modelling studies have been performed. Cobscook Bay and Toothacher Bay in Maine are studied in detail through the use of mathematical models and field data. We find that a systematic, site-specific, step-by-step modeling strategy involving the use of numerical models to simulate the overall hydrodynamic environment in combination with a waste-particle transport model can be an extremely powerful method of determining a priori whether aquaculture operations will cause high rates of net-pen waste accumulation at a particular site.     

Landslide hazard and risk assessment mapping of mountainous terrains - a case study from Kumaun Himalaya, India

Landslides are studied systematically in order to evaluate the nature of hazard and the damages to the human life, land, roads, buildings and other properties. This can be expressed in terms of risk, which is a function of hazard probability and damage potential. A risk map will indicate the priorities for landslide hazard management. A new approach to risk assessment mapping using a risk assessment matrix (RAM) is presented.     

Multiple episodes of tectonothermal processes in the Eastern Ghats granulite belt

A suite of rocks from Borra Carbonate Granulite Complex (BCGC) in the Eastern Ghats granulite belt displays superposed structures and overprinted mineral assemblages that reveal multiple episodes of tectonothermal reworking of the complex under granulite facies condition. Five distinct episodes of deformation (D₁, D₂, D₃, D₄ and D₅) and four phases of metamorphism (M₁, M₂, M₃ and M₄) are recorded. The signature of the earliest tectonothermal event, D₁ is a gneissic foliation (S₁) denned by segregation of peak granulite facies mineral assemblages corresponding to prograde M₁ metamorphism. M₂ metamorphic overprint represents an episode of near-isobaric cooling of the complex under a static condition. D₂ represents an episode of ductile deformation manifested by isoclinal folding (F₂) and associated extensional structures, within a broad framework of coaxial bulk deformation. The present study reveals that D₂ took place subsequent to M₂ - Subsequent deformation, D₃, produced F₃ folds and also deformations of boudins formed during D₂. M₃, which is synchronous with F₃, represents a near isothermal decompression of the BCGC. This was followed by a weak structural readjustment (D₄), producing E-W cross folds. The latter was not, however, associated with any recognizable petrological reworking. In the terminal events, deformation (D₅) and mineral reactions (M₄) were localized along narrow intersecting shear zones. The latter acted as channelways for carbonic and still later hydrous fluid infiltration. The available thermobarometric data from BCGC and other areas of the Eastern Ghats belt reveal that reworking during M₂ and M₃ ensued in a thermally perturbed regime. The high thermal regime might also have persisted during carbonic fluid infiltration related to terminal reworking (M₄).     

Effect of tunnel depth on modulus of deformation of rock mass

Summary Deformability of rock mass significantly influences its behaviour and is, therefore, an important consideration for the design of underground openings. The modulus of deformation of rock mass is, however, normally obtained from expensive and time-consuming uniaxial jacking tests, whose results often have a large scatter. An empirical correlation has, therefore, been proposed for a quick and inexpensive preliminary estimation of the modulus of deformation of rock mass on the basis of field instrumentation carried out in tunnels in India.     

Electron cyclotron waves in the presence of parallel electric fields in the Earth’s auroral plasma

The electron cyclotron waves that originate at low altitudes (<0.5 R_E) and observed by ground facilities have been studied in the presence of a weak parallel electric field in auroral magnetoplasma consisting of trapped energetic auroral electrons and cold background electrons of ionospheric origin. The model distribution for auroral trapped electrons is taken as Maxwellian ring distribution. An expression for the growth rate has been obtained in the presence of parallel electric field assuming that the real frequency in the whistler mode is not affected by the presence of the electric field. The results show that waves grow (or damp) in amplitude for a parallel (or antiparallel) electric field. The influence of the electric field is more pronounced at a shorter wavelength spectrum. An increase in population of energetic electrons increases the growth rate and thus, plays a significant role in the wave excitation process in the auroral regions.     

Effect of class-interval size on entropy

The value of Shannon entropy for a given set of data depends on the class interval chosen to compute the relative frequency of each class. For three data sets, expressed in dimensional as well as nondimensional form, the entropy value was computed for different class-interval sizes. Entropy was found to decrease with increasing class interval as well as with increasing sampling interval. It is suggested that these intervals should be selected with care.     

Geochemistry and petrogenesis of anorogenic basic volcanic-plutonic rocks of the Kundal area,Malani Igneous Suite,western Rajasthan,India

The Kundal area of Malani Igneous Suite consists of volcano-plutonic rocks. Basalt flows and gabbro intrusives are associated with rhyolite. Both the basic rocks consist of similar mineralogy of plagioclase, clinopyroxene as essential and Fe-Ti oxides as accessories. Basalt displays sub-ophitic and glomeroporphyritic textures whereas gabbro exhibits sub-ophitic, porphyritic and intergrannular textures. They show comparable chemistry and are enriched in Fe, Ti and incompatible elements as compared to MORB/CFB. Samples are enriched in LREE and slightly depleted HREE patterns with least significant positive Eu anomalies. Petrographical study and petrogenetic modeling of [Mg]-[Fe], trace and REE suggest cogenetic origin of these basic rocks and they probably derived from Fe-enriched source with higher Fe/Mg ratio than primitive mantle source. Thus, it is concluded that the basic volcano-plutonic rocks of Kundal area are the result of a low to moderate degree (< 30%) partial melting of source similar to picrite/komatiitic composition. Within plate, anorogenic setting for the basic rocks of Kundal area is suggested, which is in conformity with the similar setting for Malani Igneous Suite.